1. Field of the Invention
The present invention relates to an objective lens driving apparatus used with an optical pickup.
2. Description of the Related Art
In general, disk drives record and/or reproduce information to and/or from a disk or a recording medium by emitting light thereon. The disk drives include a turntable on which a disk is placed, a spindle motor rotating the turntable, and an optical pickup emitting light on a recording surface of the disk to perform recording and/or reproduction.
However, the light emitted from the optical pickup must be perpendicularly incident on the recording surface of the disk to form an accurate light spot. If the incident direction of light is inclined, an accurate light spot cannot be formed on the disk and, an error is generated in recording and reproduction of data. Thus, in order to form an accurate light spot on a desired track of a disk, the light needs to be perpendicularly incident on the recording surface of the disk. Adjusting the light to be perpendicularly incident on the recording surface of the disk is referred to as tilt adjustment or skew adjustment. Typically, an objective lens driving apparatus controls the position of an objective lens in a focusing direction and a tracking direction so that the focus of light can be accurately formed on a desired track of the recording surface of the disk. However, the objective lens driving apparatus maintains the focus of a light spot by maintaining a constant distance between the objective lens and the recording surface of the disk and controls the light spot to follow a desired track, but it does not directly control an incident angle of the light with respect to the recording surface of the disk. Thus, for more precise recording and reproduction, an operation of dynamically adjusting the tilt is needed.
To meet the needs stated above, as shown in FIGS. 1 and 2, a conventional objective lens driving apparatus of an optical pickup having a dynamic tilt adjustment mechanism has been suggested. The optical pickup shown in the drawing is an objective lens driving mechanism which includes a focus and tracking adjustment mechanism driving a blade 2 where an objective lens 1 is mounted in a focus direction A and a tracking direction B, and a tilt adjustment mechanism driving the blade 2 in a tilt direction C.
The focus and tracking adjustment mechanism has a typical structure including a focus coil 3, tracking coils 4, and a magnet 8. Thus, the focus and tracking adjustment mechanism generates an electromagnetic force to drive the blade 2 by controlling currents flowing through the focus coil 3 and the tracking coils 4. Reference numeral 5 denotes a wire supporting the blade 2 to move with respect to the holder 6.
The tilt adjustment mechanism includes steel wires 17a and 17b inserted in bosses 16a and 16b on a base 10, tilt coils 15a and 15b wound around the bosses 16a and 16b, and tilt magnets 14a and 14b installed at the blade 2 to face the steel wires 17a and 17b. Thus, the steel wires 17a and 17b are magnetized according to the direction of current flowing in the tilt coils 15a and 15b. The blade 2 is driven in the tilt direction C by the magnetic operation between the magnetized steel wires 17a and 17b and the tilt magnets 14a and 14b. 
In the above structure, since constituent elements of the tilt adjustment mechanism, such as the tilt coils 15a and 15b, are installed in an additional space on the base 10 separated from the space for the focus and tracking adjustment mechanism, it is difficult to make a compact objective lens driving apparatus. Also, since the tilt magnets 14a and 14b, which are relatively heavy bodies, are installed on the blade 2 which is a driving portion, a response speed is reduced due to the heavy weight of the driving portion. Therefore, a structure which can perform accurate lens driving control and tilt control between the disk and the optical pickup is needed.